The use of getter devices in electronic tubes is well known. A commonly used getter construction consists of a container such as a U-section ring container into which is pressed a material capable of releasing a getter metal vapour upon heating.
A particular type of electron tube which requires the use of a getter device is a television picture tube which generally comprises a neck portion which houses an electron gun structure, an enlarged bulb portion which terminates in a generally flat viewing screen, and a funnel shaped portion joining the neck and bulb portions. It is common practice to mount the getter device at the end of a spring-like metallic strip, commonly called an "antenna-spring", the other end being fixed to the electron gun structure. The spring is tensioned so that it holds the getter device against the wall of the television picture tube in the funnel portion and ensures that the getter device does not block the path of the electrons directed from the electron gun to the viewing screen.
In U.S. Pats. Nos. 3,381,805 and 3,390,758 getter devices for use in the antenna position are described which employ a ceramic member between the getter container and the tube wall to prevent problems of tube cracking which would occur if the getter container were heated, to evaporate the getter metal, while the getter container was in direct contact with the tube wall. However such getter devices are of complex structure as the ceramic member must be held to the getter container by mechanical means such as wires or bars or other securing devices. Furthermore ceramic members increase substantially the overall mass of the getter device which in turn requires that the antenna spring tension be increased. As one end of the antenna spring is attached to the electron gun structure this structure can be subjected to excessive forces which, for instance, in a colour television picture tube can cause the gun structure to be misaligned with respect to the shadow mask, resulting in a reduction of picture quality. An attempt to reduce the weight of the getter device, by using an annular ceramic member, has been proposed in U.S. Pat. No. 3,927,953. However even the provision of an annular ceramic member does not sufficiently reduce the mass of the getter device and still has the defect of being a complicated assembly.
Other getter devices have been described in U.S. Pats. Nos. 3,508,105 and 3,829,730 which employ a wire sled or support member which serves, instead of the ceramic member described above, to distance the getter container from the tube wall. While these getter devices have a relatively low mass it has still proved necessary to provide a separate tab member for attachment of the getter device to the antenna-spring and a separate member to distance the getter container away from the tube wall. However, the use of the minimum number of components in any assembly is always desirable as this reduces the assembly time and thus reduces manufacturing costs, makes automation of the assembly procedure much easier allowing greater manufacturing output at less capital outlay, furthermore it increases reliability of the product as it is less likely that there will be defective components and decreases probability that assembly defects will occur.
It is therefore an object of the present invention to provide a getter device free from one or more defects of present getter devices.
Another object of the present invention is to provide a getter device with a combined tab member and member to distance the getter container away from the electron tube wall.
A further object of the present invention is to provide a getter device using a minimum number of components.
Yet another object of the present invention is to provide a getter device having a reduced manufacturing cost.